The author probably should have made it clear that the range of the auroch got reduced over those centuries, or that, at the very least, little evidence remains. I think one reason for that (besides the rarity of finding leftover parts of dead critters from long ago, except in the case of large death assemblages) in the case of the auroch, is that it was basically a kept animal for lots of generation, and during its last 1500-2000 years in Europe, probably wasn’t just wandering around wild, or at least, not for long. :’)